6TiSCH MR. Palattella, Ed.
Internet-Draft LIST
Intended status: Informational P. Thubert
Expires: September 3, 2018 cisco
T. Watteyne
Analog Devices
Q. Wang
Univ. of Sci. and Tech. Beijing
March 2, 2018
Terms Used in IPv6 over the TSCH mode of IEEE 802.15.4edraft-ietf-6tisch-terminology-10
Abstract
This document provides a glossary of terminology used in IPv6 over
the TSCH mode of IEEE 802.15.4e (6TiSCH). This document extends
existing terminology documents for Low-power and Lossy Networks.
Status of This Memo
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6P Transaction: Part of 6P, the action of two neighbors exchanging a
6P request message and the corresponding 6P response
message.
ASN (Absolute Slot Number): The total number of timeslots that have
elapsed since the PAN coordinator has started the TSCH
network. Incremented by one at each timeslot. It is
wide enough to not roll over in practice.
BBR (Backbone Router): An LBR and also a IPv6 ND-efficiency-aware
Router (NEAR)
[I-D.chakrabarti-nordmark-6man-efficient-nd]. Performs
ND proxy operations between registered devices and
classical ND devices that are located on the backbone.
blacklist of frequencies: A set of frequencies which should not be
used for communication.
broadcast cell: A scheduled cell used for broadcast transmission.
bundle: A group of equivalent scheduled cells, i.e. cells
identified by different [slotOffset, channelOffset],
which are scheduled for a same purpose, with the same
neighbor, with the same flags, and the same slotframe.
The size of the bundle refers to the number of cells it
contains. For a given slotframe length, the size of the
bundle translates directly into bandwidth. A bundle is a
local abstraction that represents a half-duplex link for
either sending or receiving, with bandwidth that amounts
to the sum of the cells in the bundle.
CCA (Clear Channel Assessment): Mechanism defined in
[IEEE802154-2015], section 6.2.5.2. In a TSCH network,
CCA can be used to detect other radio networks in
vicinity. Nodes listen the channel before sending, to
detect other ongoing transmissions. Because the network
is synchronized, CCA cannot be used to detect colliding
transmission within the same network.
cell: A single element in the TSCH schedule, identified by a
slotOffset, a channelOffset, a slotframeHandle. A cell
can be scheduled or unscheduled.
centralized cell reservation: A reservation of a cell done by a
centralized entity (e.g., a PCE) in the network.
centralized track reservation: A reservation of a track done by a
centralized entity (e.g., a PCE) in the network.
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Channel Distribution/Usage (CDU) matrix: : Matrix of cells (i,j)
representing the spectrum (channel) distribution among
the different nodes in the 6TiSCH network. The CDU
matrix has width in timeslots, equal to the period of the
network scheduling operation, and height equal to the
number of available channels. Every cell (i,j) in the
CDU, identified by (slotOffset, channelOffset), belongs
to a specific chunk. It has to be noticed that such a
matrix which includes all the cells grouped in chunks,
belonging to different slotframes, is different from the
TSCH schedule.
channelOffset: Identifies a row in the TSCH schedule. The number of
available channelOffset values is equal to the number of
available frequencies. The channelOffset translates into
a frequency when the communication takes place, resulting
in channel hopping.
chunk: A well-known list of cells, distributed in time and
frequency, within a CDU matrix. A chunk represents a
portion of a CDU matrix. The partition of the CDU matrix
in chunks is globally known by all the nodes in the
network to support the appropriation process, which is a
negotiation between nodes within an interference domain.
A node that manages to appropriate a chunk gets to decide
which transmissions will occur over the cells in the
chunk within its interference domain (i.e., a parent node
will decide when the cells within the appropriated chunk
are used and by which node, among its children.
dedicated cell: A cell that is reserved for a given node to transmit
to a specific neighbor.
deterministic network: The generic concept of deterministic network
is defined in [I-D.ietf-detnet-architecture]. When
applied to 6TiSCH, it refers to the reservation of tracks
which guarantee an end-to-end latency and optimize the
PDR for well-characterized flows.
distributed cell reservation: A reservation of a cell done by one or
more in-network entities.
distributed track reservation: A reservation of a track done by one
or more in-network entities.
EB (Enhanced Beacon): A special frame defined used by a node,
including the JP, to announce the presence of the
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network. It contains enough information for a pledge to
synchronize to the network.
hard cell: A scheduled cell which the 6top sublayer cannot relocate.
hopping sequence: Ordered sequence of frequencies, identified by a
Hopping_Sequence_ID, used for channel hopping when
translating the channel offset value into a frequency.
IE (Information Element): Type-Length-Value containers placed at the
end of the MAC header, used to pass data between layers
or devices. Some IE identifiers are managed by the IEEE
[IEEE802154-2015]. Some IE identifiers are managed by
the IETF [I-D.kivinen-802-15-ie].
join process: The overall process that includes the discovery of the
network by pledge(s) and the execution of the join
protocol.
join protocol: The protocol that allows the pledge to join the
network. The join protocol encompasses authentication,
authorization and parameter distribution. The join
protocol is executed between the pledge and the JRC.
joined node: The new device, after having completed the join
process, often just called a node.
JP (Join Proxy): Node already part of the 6TiSCH network that serves
as a relay to provide connectivity between the pledge and
the JRC. The JP announces the presence of the network by
regularly sending EB frames.
JRC (Join Registrar/Coordinator): Central entity responsible for the
authentication, authorization and configuration of the
pledge.
LBR: Low-power Lossy Network (LLN) Border Router. It is an
LLN device, usually powered, that acts as a Border Router
to the outside within the 6TiSCH architecture.
link: A communication facility or medium over which nodes can
communicate at the link layer, the layer immediately
below IP. The IETF parlance for the term "Link" is
adopted, as opposed to the IEEE802.15.4 terminology.
pledge: A new device that attempts to join a 6TiSCH network.
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(to) relocate a cell: The action operated by the 6top sublayer of
changing the slotOffset and/or channelOffset of a soft
cell.
(to) schedule a cell: The action of turning an unscheduled cell into
a scheduled cell.
scheduled cell: A cell which is assigned a neighbor MAC address
(broadcast address is also possible), and one or more of
the following flags: TX, RX, shared, timeskeeping. A
scheduled cell can be used by the IEEE802.15.4 TSCH
implementation to communicate. A scheduled cell can
either be a hard or a soft cell.
SF (6top Scheduling Function): The cell management entity that adds
or deletes cells dynamically based on application
networking requirements. The cell negotiation with a
neighbor is done using 6P.
SFID (6top Scheduling Function Identifier): A 4-bit field
identifying an SF.
shared cell: A cell marked with both the "TX" and "shared" flags.
This cell can be used by more than one transmitter node.
A back-off algorithm is used to resolve contention.
slotframe: A collection of timeslots repeating in time, analogous to
a superframe in that it defines periods of communication
opportunities. It is characterized by a slotframe_ID,
and a slotframe_size. Multiple slotframes can coexist in
a node's schedule, i.e., a node can have multiple
activities scheduled in different slotframes, based on
the priority of its packets/traffic flows. The timeslots
in the Slotframe are indexed by the SlotOffset; the first
timeslot is at SlotOffset 0.
slotOffset: A column in the TSCH schedule, i.e. the number of
timeslots since the beginning of the current iteration of
the slotframe.
soft cell: A scheduled cell which the 6top sublayer can relocate.
time source neighbor: A neighbor that a node uses as its time
reference, and to which it needs to keep its clock
synchronized.
timeslot: A basic communication unit in TSCH which allows a
transmitter node to send a frame to a receiver neighbor,
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and that receiver neighbor to optionally send back an
acknowledgment.
track: A determined sequence of cells along a multi-hop path.
It is typically the result of a track reservation. The
node that initializes the process of establishing a track
is the owner of the track. The latter assigns a unique
identifier to the track, called TrackID.
TrackID: Unique identifier of a track.
TSCH (6top Scheduling Function Identifier): A medium access mode of
the [IEEE802154-2015] standard which uses time
synchronization to achieve ultra low-power operation, and
channel hopping to enable high reliability.
TSCH Schedule: A matrix of cells, each cell indexed by a slotOffset
and a channelOffset. The TSCH schedule contains all the
scheduled cells from all slotframes and is sufficient to
qualify the communication in the TSCH network. The
number of channelOffset values (the "height" of the
matrix) is equal to the number of available frequencies.
Unscheduled Cell: A cell which is not used by the IEEE802.15.4 TSCH
implementation.
3. Security Considerations
Since this document specifies terminology and does not specify new
procedures or protocols, it raises no new security issues.
4. References4.1. Normative References
[RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J.,
Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur,
JP., and R. Alexander, "RPL: IPv6 Routing Protocol for
Low-Power and Lossy Networks", RFC 6550,
DOI 10.17487/RFC6550, March 2012,
<https://www.rfc-editor.org/info/rfc6550>.
[RFC6552] Thubert, P., Ed., "Objective Function Zero for the Routing
Protocol for Low-Power and Lossy Networks (RPL)",
RFC 6552, DOI 10.17487/RFC6552, March 2012,
<https://www.rfc-editor.org/info/rfc6552>.
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